1. Field of the Invention
The present invention relates to a probe of an endoscope, which has an image transmitting optical system utilizing an image guide fiber bundle, and an illumination optical system utilizing a light guide fiber bundle.
2. Description of the Related Art
Usually, a medical endoscope for observing the inside of a human body, and an industrial endoscope for observing the inside of a machine, are provided with a light guide fiber bundle and an image guide fiber bundle. Namely, the inside of the body or the machine is illuminated by the light guide fiber bundle, and an image of the observed object illuminated by the light guide fiber bundle is received and transmitted to an operation unit of the endoscope by the image guide fiber bundle. The endoscopes have a probe, which is inserted into the body or the machine and which includes a flexible tube, a bendable tube, and a distal end. Namely, the inside of the probe is essentially provided with the light guide fiber bundle, and the image guide fiber bundle.
In the light guide fiber bundle, as the illumination sectional area (i.e., the sum of the sectional area of cores of optical fibers forming the light guide fiber bundle) becomes large, the amount of illumination light which can be transmitted becomes great, and thus the observed object can be illuminated with bright light. Further, in the image guide fiber bundle, as the light receiving sectional area (i.e., the sum of the sectional area of cores of optical fibers forming the image guide fiber bundle) becomes large, the amount of light which can be received becomes great, and thus a bright image can be transmitted. Namely, if the illumination sectional area of the light guide fiber bundle is made as large as possible while the light receiving sectional area of the image guide fiber bundle is made as large as possible, the observed object can be observed as a bright object.
However, the outer diameter and the inner diameter of the probe of the endoscope are limited, because of the usage of the probe, i.e., the probe is inserted into a narrow internal space of a body, a machine etc. Further, other than the light guide fiber bundle and the image guide fiber bundle, various contents including wires for bending the bendable tube, a biopsy forceps channel and air and liquid supply tubes, in the case of a medical endoscope, for example, are housed in the probe, in which the inner diameter is limited. Therefore, the sectional area of the space, in which the light guide fiber bundle and the image guide fiber bundle can occupy, is further limited.
Furthermore, in each of the guide fiber bundles, the optical fibers are bundled and fastened in a cylindrical shape at the distal end. Therefore, the sum of the outer diameters of the guide fiber bundles should be less than the inner diameter of the probe at the distal end.
Accordingly, when accommodating the light guide fiber bundle and the image guide fiber bundle, the ends of which are fastened in a cylindrical shape, in the probe in which the sectional area of the accommodation space is limited as described above, a ratio of the illumination sectional area of the light guide fiber bundle to the light receiving sectional area of the image guide fiber bundle should be optimized so as to maximize the brightness of the observed object image.
Therefore, an object of the present invention is to provide a probe of an endoscope, in which the ratio of the outer radius of the light guide fiber bundle to the outer radius of the image guide fiber bundle is optimized.
According to the present invention, there is provided a probe of an endoscope, comprising a cylindrical tube, a light guide fiber bundle, and an image guide fiber bundle. The cylindrical tube has a distal end in which an objective lens is disposed. The light guide fiber bundle is housed in the tube. A first end portion of the light guide fiber bundle, which is positioned in the distal end, is formed in a solid cylindrical shape. The light guide fiber bundle supplies illumination light to the distal end. The image guide fiber bundle is housed in the tube. A second end portion of the image guide fiber bundle, which is positioned in the distal end, is formed in a solid cylindrical shape. The image guide fiber bundle transmits an image of an observed object obtained by the objective lens. The outer radius xe2x80x9caxe2x80x9d of the second end portion and the outer radius xe2x80x9cbxe2x80x9d of the first end portion satisfy 0.545xe2x89xa6axe2x89xa60.581, 0.419xe2x89xa6bxe2x89xa60.455, and a+b=1, wherein the inner radius of the tube is supposed to be 1.
When the outer radius xe2x80x9caxe2x80x9d and the outer radius xe2x80x9cbxe2x80x9d satisfy 0.545xe2x89xa6axe2x89xa60.581, 0.419xe2x89xa6bxe2x89xa60.455, and a+b=1, and the inner diameter of the probe is fixed, the amount of light of the observed object image transmitted by the image guide fiber bundle becomes the maximum. Therefore, even though the light guide fiber bundle and the image guide fiber bundle are inserted in the probe in which the sectional area of the inner space is limited, a bright object can be effectively obtained.